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Flies in Amber Were Ancient Pollinators

In spring or summer, you can look down almost any street and see flowers blooming, on plants from dandelions to cherry trees. Flowering plants, or angiosperms, are some of the most successful and diverse forms of life on Earth. Researchers have long attributed that success, in part, to the alliances these plants have with insects that help to fertilize them by carrying pollen from one plant to another while they sip a meal of nectar.

A rendering of an extinct zhangsolvid fly and the gymnosperm plant it helped to pollinate.

It’s a win-win relationship, but new research from the American Museum of Natural History and partner institutions shows that another category of plants known as gymnosperms—the group to which modern conifers belong—also benefitted from pollination by ancient insects.

The evidence comes from a fly specimen trapped in amber during the Cretaceous Period. Researchers had previously suspected these flies, which belong to the Zhangsolvidae family, were pollinators. That’s because of their distinctive mouthparts, says David Grimaldi, a curator in the Division of Invertebrate Zoology at the Museum and coauthor on the paper, which was published in the journal Current Biology.

“These flies had specialized features like a long proboscis that was adapted to probing plants for nectar,” says Dr. Grimaldi.

What kind of plant, though, was a mystery that this research solves.

“This study presents unique, direct evidence indicating that gymnosperms were pollinated by nectivorous flies during the time of dinosaurs,” says Enrique Peñalver of the Museo Geominero in Spain, lead author on the study and previously a postdoctoral researcher at the Museum. “The exceptional preservation of these flies in amber has allowed us to discover a relationship they had with gymnosperms millions of years ago that is similar to the relationship between flies and angiosperms today.”

Flies fossilized in amber provided researchers with new insight to their feeding habits.

That direct evidence consists of a clump of pollen grains attached to the abdomen of a zhangsolvid fly. The fly was fossilized in 100-million-year-old amber from Spain, which made it easier for researchers to get a detailed look at the pollen and identify it as hailing from an extinct, conifer-like gymnosperm plant.

The scientific team could also examine the fly more closely to determine details about the specimen and learn more about its adaptations. In addition to a long “tongue,” a feature zhangsolvid flies share with modern pollinators like hawk moths and orchid bees, the flies also have wings that are well suited for hovering. That’s helpful to pollinators since getting a meal involves flying next to the same spot for a moment, as demonstrated in this animated recreation of zhangsolvid feeding.

While this study provides evidence for nectar feeding and pollination in a single species of zhangsolvid fly, Grimaldi says it is likely that other zhangsolvid flies had similar feeding methods—though they may have dined at different plants.

“Based on what we know today about long-tongued insects, different species are very specially adapted to certain plants,” says Grimaldi. “It’s likely that this fly was pretty specifically adapted, and that it wasn’t the only member of its family feeding this way.”